This proposal is designed to study the mechanism of oral tolerization to self antigen in humans with autoimmune disease. We are in a unique position in that we are presently the only group with access to patients with autoimmune diseases that have been orally tolerized to defined self antigens under controlled conditions. In addition, our laboratory has established much of the technology required to investigate the basic mechanism of oral tolerance in humans. These investigations in humans are based on experimental animal work indicating that oral tolerance is associated with both the induction of anergy and the generation of antigen specific T cells that secrete suppressive cytokines (i.e. TGFbeta and IL- 4) that down regulate inflammatory responses. These mechanisms will be directly investigated in humans using the oral administration of myelin in patients with MS and type II collagen in patients with RA. Specifically, we will examine: 1) Does oral administration of autoantigen result in specific anergy of autoreactive T cells? The precursor frequency of MBP and PLP reactive T cells will be measured by culturing with either antigen or rIL-2 before and after oral administration of myelin in patients with MS. 2) Are there changes in epitope recognition or is there T cell deletion of autoreactive T cells after oral administration of autoantigen? We will examine whether immunodominant MBP epitopes or the TCRs used to recognize these epitopes change after oral tolerization to myelin antigens. By using TCR primers specific for unique CDR3 region determinants, we will determine whether there is deletion of MBP reactive T cells. As part of specific aim 3 below, these studies will also allow us to examine whether the same T cells has switched cytokine products with oral tolerization. 3) Are there changes in the functional characteristics of autoreactive T cells after oral administration of the autoantigen? We will directly examine the cytokine profile of MBP and PLP reactive T cells after oral administration of bovine myelin in patients with MS. We postulate that MBP and PLP reactive T cells will secrete different cytokines after oral administration of myelin. 4) Does the cytokine profile change in joint tissue after oral administration of collagen type II in patients with RA? The histopathology cytokine profile as measured by intracytoplasmic staining of T cells and by quantitative PCR will be assessed in RA patients after oral administration of collagen. The results of these investigations may allow us to determine the mechanism of oral tolerance in humans with autoimmune diseases.